Justine Henin-Hardenne began defense of her U.S. Open championship Tuesday, defeating 15-year-old qualifier Nicole Vaidisova 6-1, 6-4 in a match that turned out to be more difficult than she might have expected. Seeded No. 1 and armed with the Olympic gold medal, Henin-Hardenne came in as a major favorite against the teenager from the Czech Republic, who was making her U.S.